The proposed study aims at elucidating the time relationship between tissue cAMP, cGMP levels and acid secretion in isolated, intact frog gastric mucosa during stimulation or inhibition. The secretagogues are histamine, acetylcholine and pentagastrin and the inhibitors metiamide, a H2-anagonist, and atropine an anticholinergic agent. The activation of cAMP- and cGMP-dependent protein kinases will be studied with the above mentioned secretagogues. The effect of the H2-antagonist, metiamide, on cAMP- and cGMP-dependent protein kinases will be investigated during both resting and secreting conditions. The study will also try to establish the effect of phosphodiesterase inhibitors on cAMP and cGMP levels and the activation of resp. protein kinases.